Class ExprNone

java.lang.Object
org.apache.jena.sparql.expr.ExprNode
org.apache.jena.sparql.expr.ExprNone
All Implemented Interfaces:
Expr

public class ExprNone extends ExprNode
Marker, used in place of a null. This may be tested for using ==
  • Method Details

    • visit

      public void visit(ExprVisitor visitor)
    • eval

      public NodeValue eval(Binding binding, FunctionEnv env)
      Description copied from interface: Expr
      Evaluate this expression against the binding
      Specified by:
      eval in interface Expr
      Specified by:
      eval in class ExprNode
    • hashCode

      public int hashCode()
      Description copied from interface: Expr
      Expr are used in both syntax and algebra. There is no syntax to algebra translation step because the parser uses operator precedence to build the right evaluation structure directly.

      The exceptions to this are the NOT EXISTS and EXISTS expressions which involve a query pattern. As a result there are different ways in syntax to produce the same algebra form.

      Two Expr are considered equal if they are equal as algebra expressions. hashCode and equals must implement that.

      There is also equalsBySyntax. Because two different syntax forms can yield the same algebra, but two different algebra forms must be different syntax, equalsBySyntax implies equals (by algebra).

      Hence, different hashCode => not equalsBySyntax.

      Specified by:
      hashCode in interface Expr
      Specified by:
      hashCode in class ExprNode
    • equals

      public boolean equals(Expr other, boolean bySyntax)
      Description copied from interface: Expr
      General equality operation - consider this to be 'protected'
      Specified by:
      equals in interface Expr
      Specified by:
      equals in class ExprNode
    • copySubstitute

      public Expr copySubstitute(Binding binding)
      Description copied from interface: Expr
      Deep copy with substitution
      Specified by:
      copySubstitute in interface Expr
      Specified by:
      copySubstitute in class ExprNode
    • applyNodeTransform

      public Expr applyNodeTransform(NodeTransform transform)
      Description copied from interface: Expr
      Rewrite, applying a node->node transformation
      Specified by:
      applyNodeTransform in interface Expr
      Specified by:
      applyNodeTransform in class ExprNode